1. Field of the Invention
The invention relates to a video camera having a memory for temporarily storing data of a solid state image pickup device such as a CCD or the like.
2. Related Background Art
First, the timing to drive an ordinary solid state image pickup device such as a CCD or the like is shown. FIGS. 1 and 2 show only the portions necessary for explanation. In FIG. 1, reference numeral 101 denotes a CCD having stripe color filters of R, G, and B; 102 a sample and hold circuit; and 103 a timing signal generating circuit. In FIG. 2, a denotes outputs R, G, and B of the CCD; b indicates a sampling and holding pulse which is generated from the timing signal generating circuit 103; and c indicates output signals r, g, and b after completion of the sampling and holding processes.
Hitherto, the pixel signal of one field of the solid state image pickup device 101 is read out at a period of one field of the standard system of the television. The number of pixels of the solid state image pickup device is being increased in recent years and the number of transfer pixels per one horizontal line is being increased.
When the number of transfer pixels increases, the transfer time per pixel decreases, a defective transfer occurs, the time width of an output signal per pixel of the image pickup device 101 is too short, a timing precision of the sampling and holding process becomes severe, or an A/D converter which operates at a high speed is needed in the case where the signal of the image pickup device 101 is A/D converted into the digital signal or the like.
Due to such causes, a yield of the solid state image pickup device is eventually deteriorated or peripheral circuits of the solid state image pickup device become complicated.
On the other hand, if the image signal is read out too slowly than it is needed, when the signal of the solid state image pickup device is stored into the memory, the transfer time increases. There is an inconvenience such that a continuous photographing speed becomes slow or the like as a camera.